[G0HZU_JMR]

The comms receiver was a bit strange in that it was designed mainly for receiving stuff from low cost digital transmitters that might use FSK or OOK. It was mainly a downconverter ahead of a narrow digital IF but it also needed to monitor crude (and drifty) transmit devices that had a wider bandwidth that transmitted FSK/FM. There were two wideband FM bandwidths and these both used a conventional limiter/detector instead of doing the demod in the digital domain in the narrowband IF.

It also had a wider bandwidth output that could feed to a digital IF of about 1MHz bandwidth but this was done at a previous (higher) IF frequency. All the digital IF/DSP stuff was in another box.

Quite a few of these receivers were made, probably over a hundred. I've still got some sample parts from the dev work including some very exotic KVG crystal filters. Eg I think one of them is a 21.4MHz crystal filter with 50kHz bandwidth for example. It had preselection crystal filters ahead of the narrowband digital IF. I think the selectable IF bandwidths were 10kHz, 20kHz and 50kHz and this was done using crystal filters.

It also had a hybrid DDS/PLL synthesiser that ran up at UHF that could tune in tiny steps. This was quite exotic in those days. This used the AD 9850 DDS as a tuneable reference and this DDS was a brand new part in those days. I still have one of the hybrid synthesisers here but it hasn't been used for over 20 years.